The measurement of a body temperature is useful for assessing the health of a subject. Typically, a body temperature is measured by a thermometer positioned in a body cavity, such as the mouth, the axilla, or the rectum. A core body temperature, commonly measured in the pulmonary artery, is generally considered a better indicator of a subject's health than peripheral temperatures of the aforementioned body cavities or of external locations, such as the subject's forehead or temple area.
A variety of thermometry devices are used to measure body temperatures. U.S. Pat. No. 6,280,397 to Yarden et al., whose disclosure is incorporated herein by reference, provides a high speed temperature measuring device for measuring an internal body temperature by insertion of the device into a body cavity. A heat conduction transfer equation is solved to determine the internal body temperature.
Insertion of a thermometer into a body cavity is an invasive measurement that generally causes some discomfort to the subject. Invasive measurement may also require the subject's cooperation and adherence to measurement procedures, such as keeping a thermometer tip under the tongue during oral temperature measurement. Non-invasive temperature measurement at an external measurement site, such as a subject's forehead, may be less discomforting and less dependent on subject cooperation. However, a large statistical deviation may exist between the temperature at an external measurement site and the core body temperature.
The poor correlation between external and peripheral temperatures with the core body temperature is described by Fullbrook in “Core temperature measurement: a comparison of axilla, tympanic membrane and pulmonary artery blood temperature,” Intensive Critical Care Nursing, Oct. 1997, 13(5):266-72, whose disclosure is incorporated herein by reference.
U.S. Pat. No. 6,292,685 to Pompei, whose disclosure is incorporated herein by reference, provides a method of detecting human body temperature by laterally scanning an infra-red (IR) temperature detector across a forehead and providing a peak temperature reading from multiple readings.